Applied semiconductor products are indispensable in many industrial fields. As a typical example, semiconductor chips are manufactured by slicing a silicon monocrystalline to a predetermined thickness to produce a silicon wafer; then forming a variety of circuits in a pattern shape thereon.
In order to manufacture a semiconductor chip, an electrostatic chuck for supporting a wafer, a hot plate for heating a wafer, and a wafer prober for checking whether the circuit operates in accordance with its design are needed. These may preferably be of ceramic material in terms of heat resistance and corrosion resistance.
For example, Japanese patent registration No. 2798570 discloses an electrostatic chuck made of ceramic materials having such construction as to have a heat generation body therein.
FIG. 11 is a cross sectional view showing an example of such electrostatic chuck schematically. The electrostatic chuck shown in the figure is provided therein with a RF electrode 80 and a heat generation body 82. Furthermore, the electrostatic chuck is provided therein with through-holes 84, 86 for connection respectively with the RF electrode 80 and the heat generation body 82. In fact, respective through-holes 84, 86 are formed by a sintered ceramic body of a laminated structure, which have a cylindrical shape, and being filled with conductive components. As the conductive materials, for example, tungsten is adopted. The structure of the through-holes of the electrostatic chuck are such that the electric wiring of respective layers are drawn out and/or connected to each other via an external terminal pins 88.
Accordingly, the through-holes 84, 86 are made of different materials from a sintered ceramic material from the view point of structural metallography. Additionally, a thermal expansion rate of the through-holes 84, 86 is different from that of a sintered ceramic materials. Accordingly, adhesion between tungsten and sintered ceramic materials tends to deteriorated.
Due to a long-term use, if a heat sink cycle and a thermal shock are applied to such electrostatic chuck, adhesion between the through-hole and a sintered ceramic material deteriorates. The external terminal pin is connected using a flux. The structure arises a problem such that the repeated attachment and detachment between the external terminal pin and a power supply causes a drawing force to be applied to the through-hole, thus resulting that adhesion between a through-hole and a sintered ceramic material to be deteriorated.
Such problem is not always brought to an electrostatic chuck, but also to a wafer prober having a ceramic substrate provided with electrodes therein and to a ceramic heater having a ceramic substrate provided with a heat generation body therein.
The object of the present invention is to provide a ceramic substrate which is provided with a through-hole having an excellent tolerance against a drawing stress applied to an external terminal pin, the ceramic substrate being for use in an inspection device for use in processes of manufacturing semiconductors.